This invention relates generally to a mirror assembly having a reflective surface that is spatially adjustable so as to have its orientation changed by an operator who is located at a remote location with respect to the assembly; more specifically, the invention relates to a mirror assembly of the type that is commonly put on large vehicles (e.g., large trucks and buses) to serve as a selectively adjustable rearview mirror.
The problems associated with providing dependable rearview mirrors for large vehicles are well known. Such large vehicles include: buses; tractors of the type that are commonly used to pull semi-trailers (the combination often being referred to as "tractor/trailer rigs"); motor homes; and large trucks, e.g., class 8 trucks. Most of these large vehicles do not have rear windows through which a driver might obtain a direct line of sight to the rear of the vehicle. So whatever knowledge a driver obtains about conditions to the rear of the vehicle is obtained from looking at rearview mirrors. Because the number of such large vehicles on public roads is great, and the hazards associated with operation of such large vehicles are equally great, there have been many proposed solutions for providing drivers with improved vision to their rear, especially on the right side of the vehicle (when the steering wheel is on the left side). Examples of rearview mirrors which are selectively adjustable about a generally vertical axis are found in the following U.S. patents: U.S. Pat. Nos. 3,416,854 to Fykes titled "Remotely Adjustable Rear View Mirror With Pneumatic Operator"; 3,610,736 to Bateman titled "Power-Driven Rear View Mirror"; 3,815,365 to House titled "Control For Rearview Mirror"; and 3,830,561 to LaFave et al. titled "Remotely Operable Vehicular Mirror".
While some of the above-identified patents have proposed solutions that are better than fixed external mirrors, they do not address all of the problems that are faced by a driver who is attempting to maneuver a large vehicle in a confined area. Furthermore, changes in the average physical characteristics of truck drivers have introduced a requirement that is not new, but which is becoming more significant, namely, the physical size of drivers. Many trucking companies are now hiring female drivers--who are typically shorter than most males, and Oriental drivers--who are typically shorter than most Occidentals. The designers of trucks can no longer act on the assumption that the average truck driver will be about 5 foot, 11 inches in height and weigh 200 pounds, and then design a vehicle's cab to "fit" such a hypothetical person. And many driver teams are now made up of husbands and their wives, with the result that a rearview mirror adjusted to suit a husband's line of sight to the rear of a vehicle may not be appropriate for a shorter wife--who may also drive the vehicle. Prudence therefore dictates that a truly serviceable rearview mirror for trucks and the like must be capable of adjustment about a generally horizontal axis as well as a generally vertical axis.
The idea of providing a four-way mirror, i.e., one that can rotate in two directions about two orthogonal axes, is itself not new. Examples of proposed four-way mirrors can be found in the following U.S. patents: U.S. Pat. Nos. 4,639,103 to Hill titled "Remote Control Multi-Position Rear View Mirror"; and 5,082,361 to McKee titled "Horizontally and Vertically Movable Remote Controlled Mirror Unit For Commercial Vehicles". But while these patents may have taught that it is desirable to achieve movement in tour directions (i.e., right and left, up and down), they have not solved all of the problems associated with such movement. For example, the Hill patent teaches a mirror that is selectively movable to any one of four pre-selected positions, but it is impossible to achieve an intermediate location between any of the four fixed positions. The McKee patent identifies the benefits of a four-way mirror, but it does not explain how to achieve those benefits. That is, there is no teaching in McKee of what kind of drive mechanism might find utility in reaching the announced goal of producing an operable four-way mirror.
Furthermore, the four-way mirrors that have actually reached the marketplace do not have a good reputation for overcoming a major nemesis of mirrors on large vehicles, namely, vibration. The gross weight of 18-wheel tractor/trailer rigs can range from 30,000 to 100,000 pounds and have large Diesel engines that are capable of generating on the order of 450 horsepower at about 2100 to 2500 RPM. And the vibrations associated with such large vehicles when the engine is running can be enough to render an image in an external mirror so "bouncy" as to make it useless to a driver. Besides being severe in the short term, vibrations associated with a vehicle engine and road conditions can also be problematical because of their duration. It is not unusual for a long-haul driver to put 250,000 miles per year on a tractor that is pulling trailers across the country on interstate highways. It is therefore a goal of this invention to provide a crisp, stable image in a remotely controlled mirror, which mirror is capable of being selectively rotated about at least one axis and preferably two orthogonal axes.
It is probably worthy of mention that automobile mirrors have been around for quite some time, and for several years there have been electro-mechanical mirrors that are capable of being pivoted about two orthogonal axes. But there are two major factors that preclude the direct transfer of successful automobile technology to trucks, namely, weight and geometry. Many truck mirrors utilize a piece of flat glass that is 7" by 16", which makes them about three times larger than even the biggest automotive mirrors. And with the increase in size there is, of course, a concomitant increase in weight. Also, truck mirrors are traditionally mounted on C-shaped brackets in which two generally horizontal arms extend outwardly from a truck cab for distances ranging from 10" to 20". These two horizontal arms are required to support a vertically oriented mirror assembly between them at their distal ends: and a force analysis on such a construction would almost be equivalent to that of two cantilevered beams that are holding a heavy weight between them. Therefore, the typical mounting system for a truck mirror tends to behave like a heavy mass suspended between two springs; and the truck vibrations that are generated both at idle and when travelling tend to produce vibrations in the mirror-mounting system that can be so severe as to interfere with any beneficial use of the mirror. It is therefore an object of this invention to provide an improved mirror assembly for large trucks, etc., that is capable of providing stable images that provide meaningful information to a driver.
Still another object is to provide a mirror that is capable of being manually adjusted by a driver by simply pushing on the reflective surface--in the event that a power-assisted mechanism (which is normally used to adjust the mirror's orientation) becomes inoperative. Those skilled in the art will recognize, of course, that this is a commendable goal, because the laws of many states require that rearview mirrors must be serviceable before a truck can be moved on a state's highways. So if a failure should occur in the power mechanism, and the truck was being inspected at one of the many truck inspection stations along our highways, at least the driver could continue on his run. He would only need to manually place the mirror where it will do what old-fashioned, fixed mirrors have done in the past, namely, provide a fixed field of view to the driver with regard to the rear of the truck or trailer. And pushing directly on the reflective surface to correctly orient the mirror will not cause damage or breakage of any internal pans of the power mechanism.
A further object is to provide a power-assisted arrangement for adjusting remote-controlled mirrors with hydraulics, but which uses a system that does not remain pressurized when adjustment of the mirror's orientation is not taking place.
One more object is to provide a four-way mirror that is capable of being moved to almost an infinite number of positions between full right and full left, and between full up and full down.
These and other objects will be apparent from a careful reading of the specification and the concluding claims, together with reference to the several figures of the drawing that are provided herewith.